254 G. E. (JOOHILL 



The Gasserian ganglion, also, has migrated towards the bi-ain. 

 The infraorbital trunk can be traced approximately to the ventral 

 margin of the primordium of the nmscles of mastication (fig. 

 3, Mdb.) It now passes through a distinct groove in this pri- 

 mordium. As it leaves this groove it gives oE the ramus maxil- 

 laris (Mx.V) which passes only a short distance forward under 

 the eye. No fibers from the r. mandibularis can be traced into 

 the balancer at this stage. The fibers to the skin in the post- 

 optic region are still less obvious than they are in front of the 

 eye, but favorable preparations show that they are present. 



Figure 33 illustrates the trigeminal root as it enters the brain. 

 The plane of section of this figure may be judged by figure 17, 

 in which the area of figure 33 is blocked out and marked a. 

 This plane of section will be recognized as inclined cephalo-ventrad 

 in a longitudinal direction. The small ascending division of the 

 root (Tr.Asc.V) can be recognized in the figure and the appear- 

 ance of the ascending tract in transverse section is shown in 

 figure 34, which is 56 ^ rostrally of the entrance of the root. Here 

 the ascending fibers are found scattered through a considerable 

 area dorso-ventrally. The descending division of the root (fig. 

 33, Tr.Des.B) is much more massive than the ascending, and 

 extends caudad to about the level of the facial root, as shown in 

 figure 5, sketched in solid black. The tract which is labeled 

 Tr.Des.V. in figures 38 to 49 is apparently composed at these 

 various levels of processes of central neurones. Its fibers are 

 scattered through a considerable area dorso-ventrally and as such 

 a diffuse system may be followed on caudad into the spinal 

 cord. 



The giant ganglion cell component of the nerve is more obvious 

 in this than in earlier stages. In figure 33 one of these ganglion 

 cells (DC) appears in the angle of birfurcation of the root of the 

 ganglionic component. The cell boundaries are here clearly 

 defined. The plane of section, already mentioned as illustrated 

 in figure 17, is such that the rostral (right) end of the figure is 

 considerable more ventral then the caudal (left) end, and motor 

 cells appear in the more ventral portion of the figure {Nuc.vis.m.). 

 In figures 35, 36 and 37, three successive sections in the trans- 



